A shaft sealing device is provided around a rotor in rotary machines, such as a gas turbine and a steam turbine, in order to reduce the leakage amount of a working fluid that flows from a high-pressure side to a low-pressure side. As an example of the shaft sealing device, the shaft sealing device described in the following Patent Document 1 is known.
The shaft sealing device includes a housing provided in a stator, and a sealing body constituted by multiple thin sealing pieces.
In the sealing body, the multiple thin sealing pieces are stacked with small clearances therebetween so that the thickness direction of each thin sealing piece is directed to the circumferential direction of the rotor. The respective thin sealing pieces are obliquely arranged so that the end portions (tips) thereof on a radially inward side are located further toward the front side in the rotational direction of the rotor than the end portions (rear ends) of the thin sealing pieces on a radially outward side, to be coupled to each other at the rear ends thereof, and the tips of the thin sealing pieces are free ends.
In the shaft sealing device configured in this way, the tip of each thin sealing piece comes into contact with the rotor when the rotor remains stationary. If the rotor rotates, the tip of the thin sealing piece is lifted from the outer periphery of the rotor by a dynamic pressure effect produced by the rotation of the rotor, and comes out of contact with the rotor. For this reason, in the shaft sealing device, wear of each thin sealing piece is suppressed, and the service life of a seal is extended.
Moreover, the shaft sealing device is provided with a low-pressure-side side sealing plate that covers the low-pressure side of the sealing body in the circumferential direction, and a high-pressure-side side sealing plate that covers a high-pressure side of the sealing body in the circumferential direction. By adjusting the radial dimensions of the low-pressure-side side sealing plate and the high-pressure-side side sealing plate, the sizes of a space on the high-pressure side of the thin sealing piece and a space on the low-pressure side thereof are specified and the gas pressure distribution of a small clearance is set so as to assist a lifting force generated by the above-described dynamic-pressure effect.